Naringenin Regulates Expression of Genes Involved in Cell Wall Synthesis inHerbaspirillum seropedicae

Abstract

Five thousand mutants of Herbaspirillum seropedicae SmR1 carrying random insertions of transposon pTnMod-OGmKmlacZ were screened for differential expression of LacZ in the presence of naringenin. Among the 16 mutants whose expression was regulated by naringenin were genes predicted to be involved in the synthesis of exopolysaccharides, lipopolysaccharides, and auxin. These loci are probably involved in establishing interactions with host plants.The betaproteobacterium Herbaspirillum seropedicae is an endophytic diazotroph that forms nitrogen-fixing associations with maize (Zea mays), rice (Oryza sativa), sorghum (Sorghum bicolor), and sugar cane (Saccharum officiarum), as well as such diverse plants as bananas (Musa spp.) and pineapple (Ananas comosus) (1, 5, 27). As such, H. seropedicae is a potential nitrogen biofertilizer that also produces phytohormones that may stimulate the growth of plants (4). Studies demonstrated that the inoculation of rice with H. seropedicae promoted a yield increase equivalent to treatment with 40 kg N/ha (2). Coinoculation of micropropagated sugar cane with Gluconacetobacter diazotrophicus and Herbaspirillum sp. resulted in an increase of the total plant biomass (25).Exactly how H. seropedicae colonizes Gramineae and other plants is not known, and there is even less information available on the role of plant metabolites in the regulation of bacterial invasion and colonization of the inner tissues. That such associations involve molecular communication between the host plant and bacteria, resulting in modified patterns of gene expression, is clear from studies of other rhizospheric bacteria (15). In legume-Rhizobium interactions, flavonoids released by plant roots induce sets of genes involved in nodulation. As a result, lipochitooligosaccharides are excreted and symbiotic forms of exopolysaccharides (EPSs), lipopolysaccharides (LPSs), and glucans synthesized, all of which modulate the nodulation process (8,15,26). Previous studies showed that naringenin (50 mol/liter) stimulated the root colonization of Arabidopsis thaliana by H. seropedicae (16) and the intercellular colonization of wheat roots by Azorhizobium caulinodans (33).To identify bacterial genes whose expression is under the control of the flavonoid naringenin, the chromosome of H. seropedicae strain SmR1 (23) was randomly mutagenized using a lacZ-Km-Gm cassette carried by the plasmid pTnModOGmKmlacZ, and strains resistant to both kanamycin and gentamicin were selected (30). Twelve thousand mutant strains were obtained, and 5,000 screened for differential expression of the promoterless lacZ reporter gene in the presence of naringenin (50 mol/liter) using NFbHP-malate-agar medium (19) containing X-Gal (5-bromo-4-chloro-3-indolyl-␤-D-galactopyranoside) (30 g/ml). One hundred ninety-six mutants bearing mutated genes potentially controlled by naringenin were preselected, and their ␤-galactosidase activities determined (7,24). Of these, 16 isolates carried mutated genes that reacted differently to the presence of naringenin: 4...

A Review on Pharmacological and Analytical Aspects of Naringenin

“…(66) In another study, fi ve thousand mutants of Herbaspirillum seropedicae SmR1, carrying random insertions of transposon pTnModOGmKmlacZ, were screened for differential expression of LacZ in the presence of naringenin. (67) Trans-flavonoids including naringenin have been reported as mammalian α-amylase inhibitors, a property which could be useful in the management of postprandial hyperglycemia in diabetes and related disorders. (68) Protective effects of several phenolic antioxidants, including naringenin, against the DNA-damaging effect of idarubicin originating from its P450 reductase-catalyzed bioactivation was also investigated in another study.…”

Molecular adaptations of Herbaspirillum seropedicae during colonization of the maize rhizosphere

“…Changes in the cell surface are documented in bacteria that interact with plants (D'Haeze and Holsters, 2004;Broughton et al, 2006). Tadra-Sfeir et al (2011) reported that the presence of the flavonoid naringenin caused modification of the H. seropedicae envelope structure, suggesting that plant-derived signals such as flavonoids modulate bacterial gene expression to establish an interaction with plants. Attachment of H. seropedicae SmR1 onto maize roots was shown to be mediated by binding of bacterial LPS to root lectins.…”

Root exudate profiling of maize seedlings inoculated with Herbaspirillum seropedicaeand humic acids

“…Gough et al [29] showed that flavonoids promote endophytic colonization of Arabidopsis thaliana (L.) Heynh. roots by H. seropedicae, and Tadra-Sfeir et al [30] demonstrated that naringenin (a flavonoid in the flavonone class) is involved in the gene expression of cell wall components (EPS, LPS) and auxins. In addition to its role in the genetic modulation of cell wall assembly, H. seropedicae has an operon associated with the degradation of aromatic compounds [31].…”